Patent Application
20250187372
The present application is a continuation application of International Application No. PCT/IB2023/058352, filed on Aug. 22, 2023, which claims priority to Netherlands Patent Application No. 2032814, filed on Aug. 22, 2022, the entire contents of which are hereby incorporated by reference.
The present disclosure relates to an actuator for a wheel suspension for a vehicle. The disclosure relates particularly to an actuator for wheel suspension having at least a variable track width which is adjustable between a narrow track and a wide track.
WO2016058060 A1 describes a wheel suspension comprising a frame suitable for connection to a body of a vehicle and comprising a first and second wheel which together define a track width. The first wheel is connected to the frame via a first set of actuators and the second wheel is connected to the frame via a second set of actuators such that by means of operating the actuators the track width is adjustable between a narrow track, wherein the first set of actuators overlaps in the transverse direction of the vehicle with the second set of actuators.
In practice some of the actuators will be subjected to side forces because the actuators can be fixed at various locations to for example either the frame, a knuckle, a suspension arm, or a further actuator, in such a way that the actuators a substantially horizontally orientated. The side forces are angled with respect to the movement direction of the actuators, hence their denomination.
The actuator comprises a housing having a housing wall, an electric motor mechanically coupled to a screw assembly having a screw and an associated screw nut; wherein the electric motor is configured for rotating the screw around its axis causing the screw nut to linearly move along the axis of the screw. The actuator comprises a piston rod assembly slidably coupled to the housing, wherein the piston rod assembly comprises a piston rod arranged at a predetermined distance from the housing wall such that a first cavity is formed between the piston rod and the housing wall, and wherein the piston rod assembly delimits a second cavity configured to house the screw assembly. The screw nut is coupled to the piston rod assembly such that the linear movement of the screw nut causes the piston rod assembly to be moved between a retracted position and an extended position, wherein in the extended position the piston rod assembly protrudes substantially outward from the housing. To increase longevity and provide optimal performance, particularly because the side forces cause substantial wear if the actuator is incorrectly maintained, the first cavity and the second cavity are provided with a fluid comprising at least a gaseous phase and a liquid phase.
Various approaches have been evaluated but none provide a robust and operationally reliable way of lubricating the actuators. Lubricating the actuator using nipples is such an approach but requires a substantial amount of maintenance and is operationally less reliable, particularly because such an approach requires maintenance at regular intervals. External lubrication systems are not robust and a breakdown thereof substantially reduces longevity of the actuators. Also, external lubrication systems are expensive and complex to implement in a wheel suspension having variable track width. CN111288135 and EP2491273 describe actuators having a means for lubrication.
It is an object of the disclosure to propose an actuator having a robust and operationally reliable way of lubricating itself in a selfsustained manner.
The disclosure provides for this purpose an actuator characterized by having a fluid exchange means configured to exchange at least part of the fluid between the first cavity and second cavity based on the movement of the piston.
The advantage hereof is based on the insight that the combination of rotational movement and linear movement of the actuator, for example by moving from the retracted to the extended position to turn a vehicle, changes the respective volumes of the first cavity and the second cavity. The volume of the first cavity is proportional to the position of the piston rod assembly in the housing. The volume of the first cavity is also proportional to a difference of an outside surface area of the piston rod assembly with respect to an inner surface area of the housing wall, i.e. the sides of the piston rod assembly and the housing wall delimiting the first cavity. Particularly, the volume of the first cavity when the piston rod assembly is situated in the retracted position is larger than the volume of the first cavity when the piston rod assembly is in the extended position. This difference in volume of the first cavity in the retracted position and the extended position, particularly, a reduction of volume when moving from the retracted to the extended position, pressurizes the fluid in the first cavity. Meanwhile, the volume of the second cavity proportionally and inversely changes with respect to the volume of the first cavity. The volume of the second cavity thus enlarges when the piston rod assembly moves from the retracted position to the extended position. The enlarging volume of the second cavity reduces the pressure of the fluid in the second cavity. In this way a differential pressure is created between the first cavity and the second cavity when the piston rod assembly is moved. The differential pressure causes the fluid to be moved from the cavity having the higher pressure to the cavity having the lower pressure. It will be apparent that moving from the extended to the retracted position enlarges the volume of the first cavity, respectively reduces the volume of the second cavity and the above-mentioned differential pressure is inverse causing the fluid to flow from the second cavity to the first cavity. The differential pressure caused by moving the piston rod assembly during operation thus provides an easy, robust and selfsustained way of reliably lubricating the actuator.
Preferably, the fluid exchange means comprises a first fluid channel and a second fluid channel formed in the piston and which respectively fluidly connect the first cavity and the second cavity. The first and second fluid channel allow the fluid to flow from the first cavity to the second cavity and vice versa in a relatively simple manner. More preferably, the first and second fluid channel comprise a cross-sectional area of at least 0.5 mm2, preferably at least 10 mm2. The inventors have found that the first and second fluid channel comprising a cross-sectional area of at least 0.5 mm2 provides a balanced differential pressure and flow rate between the first and second cavity. More preferably, the first fluid channel and the second fluid channel are an aperture through the piston wall. Such an aperture is robust, easily manufacturable and in a situation where maintenance of the actuator is required easily cleanable.
Preferably, the fluid exchange means further comprises a first shut-off means and a second shut-off means correspondingly arranged such that the first shut-off means allows fluid to flow from the first cavity to the second cavity through the first fluid channel and inhibits flow from the second cavity to the first cavity and such that the second shut-off member only allows fluid to flow from the second cavity to the first cavity through the second channel. In this way a circular flow of the fluid is created inside the actuator. The circular flow is advantageous because the fluid is forced in a direction reducing stagnation of the fluid in certain locations, this improves lubrication of the actuator.
Preferably, the first fluid channel and corresponding first shut-off means are arranged at an upper segment of the piston wall, preferably an uppermost segment, and wherein the second fluid channel and corresponding first shut-off means are arranged at a lower segment of the piston wall, preferably a lowest segment. An advantageous hereof is based on the insight that the actuators arranged in a wheel suspension having variable trackwidth are typically oriented in a substantially horizontal way. By providing the first fluid channel and corresponding first shut-off means and the second fluid channel and corresponding second shut-off means in an uppermost segment and a lower segment the circular flow comprises an upward and downward component in that the movement of the actuator to the extended position forces the fluid upward, through the first fluid channel into the second channel. Similarly, when moving from the extended position to the retracted position, the fluid is forced downward from the second cavity, through the second fluid channel into the first cavity.
Preferably, the first shut-off means covers the first fluid channel and is arranged on a side of the piston wall delimiting the second cavity and where the second shut-off means covers the second fluid channel and is arranged on a side of the piston wall delimiting the first cavity. Preferably, the first shut-off means and the second shut-off means are made from a resilient material. In this way, the fluid can open the fluid channels when pressure is exerted from one side of the shut-off means. The resiliency of the shut-off means allows the shut-off means to open the fluid channel by bending in a direction away from the exerted pressure. Additionally, the resiliency of the shut-off means also allows the shut-off means to shut the fluid channels when the direction of the pressure on the fluid is reversed, for example when the second cavity is pressurized with respect to the first cavity. More preferably, the resilient material is an elastomer.
Preferably, the piston rod has a proximal end and a distal end, wherein the fluid exchange means are arranged near the proximal end of the piston rod. In this way, the fluid exchange means are allowed maximum travel within the actuator and thus also circulate a maximum amount of fluid with respect to that actuator.
Preferably, the actuator further comprises a set of bearings arranged between the housing and the piston, wherein the set comprises a first bearing and a second bearing, wherein the first bearing is arranged at a proximal end of the piston, and wherein the second bearing is at a distal end of the piston, wherein the set of bearings is configured to slidably support the piston rod assembly in the housing.
Preferably, the actuator further comprises a seal arranged between the piston and the housing. Even though the first and second cavity are fluidly connected, the seal inhibits the fluid from flowing through other openings, such as the opening between the piston and the housing. This improves the lubrication of the actuator further.
Preferably, the actuator further comprises a further seal arranged between the electric motor and the second cavity, which further seal is configured to substantially prevent fluid from flowing from the second cavity to the electric motor. Although the fluid can be used to cool the electric motor, it is preferred that the fluid is retained in the first and second cavity.
Preferably, the actuator further comprises a first connection means and a second connection means respectively arranged at a proximal end and a distal end of the actuator such that the actuator is pivotably connectable any one of a vehicle frame, a suspension strut and a knuckle.
Preferably, the actuator further comprises a suspension strut support arranged at a distal end of the housing, which suspension struct support is configured to rigidly support a suspension support.
The accompanying drawings are used to illustrate presently preferred non-limiting exemplary embodiments of devices of the present disclosure. The above and other advantages of the features and objects of the disclosure will become more apparent, and the disclosure will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which:
The actuator 100 further comprises an electric motor 120. The electric motor 120 is preferably arranged near the proximal end P of the actuator 100. The electric motor 120 is mechanically coupled to a screw assembly. The screw assembly has a screw 130 and an associated screw nut 140. The screw 130 is preferably a cylindrical shaft with a thread provided on its outer wall. The associated screw nut 140 comprises a through hole through which the screw passes. On an inside of the through-hole a thread or other guidance is provided which corresponds to the thread of the screw 130. When the electric motor 120 rotates the mechanical coupling rotates the screw 130 around its axis, causing the screw nut 140 to linearly move along the axis of the screw. In other words, the screw converts a rotational motion of the electric motor 120 to a linear motion of the screw nut 140.
The actuator 100 further comprises a piston rod assembly 150 slidably coupled to the housing 110. The piston rod assembly 150 comprises a piston rod tube 151 arranged at a predetermined distance from the housing wall 111. The predetermined distance I measured radially from the centre of the actuator 100. Because the piston rod tube 151 is arranged at a distance from the housing wall 111 a first cavity A is formed between the piston rod tube and the housing wall. From
Moreover, the first cavity A and the second cavity B are provided with a fluid comprising at least a gaseous phase and a liquid phase. The liquid phase of the fluid can be a lubricating oil, whereas the gaseous phase can be dryed air or an inert gas such as nitrogen. The actuator 100 further comprises a fluid exchange means 160, 165 configured to exchange at least part of the fluid between the first cavity A and second cavity B based on the movement of the piston rod assembly 150. By moving the piston rod assembly 150 from the retracted to the extended position for example to turn a vehicle, changes the volumes of the first cavity A and the second cavity B relative to each other because the volume of the first cavity A is proportional to the position of the piston rod assembly 150 in the housing 110. Particularly, the volume of the first cavity A when the piston rod assembly is situated in the retracted position is larger than the volume of the first cavity A when the piston rod assembly is in the extended position. This difference in volume of the first cavity in the retracted position and the extended position, particularly, a reduction of volume when moving from the retracted to the extended position, pressurizes the fluid in the first cavity A. Meanwhile, the volume of the second cavity B proportionally and inversely changes with respect to the volume of the first cavity A because the volume of the second cavity B enlarges when the piston rod assembly 150 moves from the retracted position to the extended position. The enlarging volume of the second cavity B reduces the pressure of the fluid in the second cavity. In this way a differential pressure is created between the first cavity A and the second cavity B when the piston rod assembly 150 is moved. The differential pressure causes the fluid to be moved from the cavity having the higher pressure to the cavity having the lower pressure. It will be apparent that moving from the extended to the retracted position enlarges the volume of the first cavity A, respectively reduces the volume of the second cavity B and the above-mentioned differential pressure is inversed causing the fluid to flow from the second cavity B to the first cavity A. The differential pressure caused by moving the piston rod assembly 150 during operation thus provides an easy, robust and selfsustained way of reliably lubricating the actuator 100.
According to a further preferred embodiment the actuator 100 further comprises a set of bearings 181, 182 arranged between the housing 110 and the piston rod assembly 150. The set comprises a first bearing 181 and a second bearing 182, wherein the first bearing 181 is arranged near a proximal end 151p of the piston wall 151, and the second bearing 182 is arranged near a distal end 151d of the piston rod. This allows to slidably support the piston rod assembly 150 in the housing 110.
The first fluid channel 160 and a second fluid channel 165 respectively fluidly connect the first cavity A and the second cavity B. The first and second fluid channel 160, 165 allow the fluid to flow from the first cavity A to the second cavity B and back in a relatively simple manner. The first fluid channel 160 and the second fluid channel 165 are preferably an aperture through the piston, as illustrated in
The enlarged view of
The fluid exchange means further comprises a first shut-off means 170 and a second shut-off means 175 correspondingly arranged such that the first shut-off means 170 substantially exclusively allows fluid to flow from the first cavity A to the second cavity B through the first fluid channel and such that the second shut-off member 175 substantially exclusively allows fluid to flow from the second cavity B to the first cavity A through the second channel. Put differently, the first shut-off means 170 inhibits the fluid to flow from the second cavity B to the first cavity through the first fluid channel 160. The second shut-off means 175 inhibits the fluid to flow from the first cavity A to the second cavity B through the second fluid channel 165.
Preferably, the first fluid channel 160 and corresponding first shut-off means 170 are arranged at an upper segment of the piston, preferably an uppermost segment. The second fluid channel 165 and corresponding first shut-off means 175 are preferably arranged at a lower segment of the piston, preferably a lowest segment. An advantageous hereof is based on the insight that the actuator 100 arranged in a wheel suspension having variable trackwidth are typically oriented in a substantially horizontal way. By providing the first fluid channel 160 and corresponding first shutoff means 170 and the second fluid channel 165 and corresponding second shut-off means 175 in an uppermost segment and a lower segment the circular flow comprises an upward and downward component in that the movement of the actuator 100 to the extended position forces the fluid upward, through the first fluid channel into the second channel. Similarly, when moving from the extended position to the retracted position, the fluid is forced downward from the second cavity B, through the second fluid channel 165 into the first cavity A.
The description and drawings merely illustrate the principles of the present disclosure. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the present disclosure and are included within its scope. Furthermore, all examples recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the present disclosure and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples thereof, are intended to encompass equivalents thereof.
It should be noted that the above-mentioned embodiments illustrate rather than limit the present disclosure and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word “comprising” does not exclude the presence of elements or steps not listed in a claim. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The present disclosure can be implemented by means of hardware comprising several distinct elements and by means of a suitably programmed computer. In claims enumerating several means, several of these means can be embodied by one and the same item of hardware. The usage of the words “first”, “second”, “third”, etc. does not indicate any ordering or priority. These words are to be interpreted as names used for convenience.
In the present disclosure, expressions such as “comprise”, “include”, “have”, “may comprise”, “may include”, or “may have” indicate existence of corresponding features but do not exclude existence of additional features.
Whilst the principles of the present disclosure have been set out above in connection with specific embodiments, it is to be understood that this description is merely made by way of example and not as a limitation of the scope of protection which is determined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2032814 | Aug 2022 | NL | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/IB2023/058352 | Aug 2023 | WO |
| Child | 19060768 | US |
